Unmapped region visualization

ABSTRACT

A method, including capturing, from an imaging system, a three-dimensional (3D) image of a body cavity, and using the captured 3D image to construct a simulated surface of the body cavity. A probe having a location sensor is inserted into the body cavity, and in response to multiple location measurements received from the location sensor, multiple positions are mapped within respective regions of the body cavity so as to generate respective mapped regions of the simulated surface. Based on the simulated surface and the respective mapped regions, one or more unmapped regions of the simulated surface are delineated, and the simulated surface of the body cavity is configured to indicate the delineated unmapped regions.

FIELD OF THE INVENTION

The present invention relates generally to medical imaging, andspecifically to using a medical probe to map a surface of a cavity of abody organ.

BACKGROUND OF THE INVENTION

A wide range of medical procedures involve placing objects, such assensors, tubes, catheters, dispensing devices, and implants, within thebody. Real-time imaging methods are often used to assist doctors invisualizing the object and its surroundings during these procedures. Inmost situations, however, real-time three-dimensional imaging is notpossible or desirable. Instead, systems for obtaining real-time spatialcoordinates of the internal object are often utilized.

U.S. Patent Application 2007/0016007, to Govari et al., whose disclosureis incorporated herein by reference, describes a hybrid magnetic-basedand impedance-based position sensing system. The system includes a probeadapted to be introduced into a body cavity of a subject.

U.S. Pat. No. 6,574,498, to Gilboa, whose disclosure is incorporatedherein by reference, describes a system for determining the position ofa work piece within a cavity of an opaque body. The system claims to usea transducer that interacts with a primary field, and severaltransducers that interact with a secondary field.

U.S. Pat. No. 5,899,860, to Pfeiffer, et al., whose disclosure isincorporated herein by reference, describes a system for determining theposition of a catheter inside the body of a patient. A correctionfunction is determined from the difference between calibration positionsderived from received location signals and known, true calibrationpositions, whereupon catheter positions, derived from received positionsignals, are corrected in subsequent measurement stages according to thecorrection function.

Documents incorporated by reference in the present patent applicationare to be considered an integral part of the application except that tothe extent any terms are defined in these incorporated documents in amanner that conflicts with the definitions made explicitly or implicitlyin the present specification, only the definitions in the presentspecification should be considered.

The description above is presented as a general overview of related artin this field and should not be construed as an admission that any ofthe information it contains constitutes prior art against the presentpatent application.

SUMMARY OF THE INVENTION

There is provided, in accordance with an embodiment of the presentinvention a method, including capturing, from an imaging system, athree-dimensional (3D) image of a body cavity, constructing, using thecaptured 3D image, a simulated surface of the body cavity, inserting aprobe having a location sensor into the body cavity, mapping multiplepositions within respective regions of the body cavity, in response tomultiple location measurements received from the location sensor, so asto generate respective mapped regions of the simulated surface,delineating, based on the simulated surface and the respective mappedregions, one or more unmapped regions of the simulated surface, andconfiguring the simulated surface of the body cavity to indicate thedelineated unmapped regions.

In some embodiments, the imaging system may be selected from a listincluding a magnetic resonance imaging system and a computed tomographysystem. In additional embodiments, the method may include presenting animage of the configured simulated surface on a display, and in furtherembodiments the image may be selected from a list including at least oneof the one or more unmapped regions and the respective mapped regions.

In some embodiments, the probe may include an intracardiac catheter, andthe body cavity may include a chamber of a heart. In additionalembodiments, the catheter may include a force sensor positioned at adistal end of the catheter, and mapping a given position may includereceiving a given location measurement upon receiving, from the forcesensor, a force measurement indicating a contact between the distal endand endocardial tissue in the chamber.

In some embodiments, configuring the simulated surface may includeassociating a visual design with the unmapped regions, and overlayingthe visual design on the unmapped regions of the simulated surface. Inadditional embodiments, the visual design may be selected from groupincluding a shading, an intensity and a pattern.

In some embodiments, delineating the one or more mapped regions mayinclude subtracting the respective mapped regions from the simulatedsurface. In additional embodiments, the location sensor may include anelectrode attached to the probe, and mapping the multiple positions mayinclude measuring impedances to a current transmitted through theelectrode. In alternative embodiments, the location sensor may include amagnetic field sensor, and mapping the multiple positions may includemeasuring magnetic fields using the magnetic field sensor.

There is also provided, in accordance with an embodiment of the presentinvention an apparatus, including a probe, configured for insertion intoa body cavity of a patient and including a location sensor for measuringa position of a distal end of the probe inside the body cavity, and aprocessor configured to capture, from an imaging system, athree-dimensional (3D) image of the body cavity, to construct, using thecaptured 3D image, a simulated surface of the body cavity, to map, whileinserting the probe into the body cavity, multiple positions withinrespective regions of the body cavity, in response to multiple locationmeasurements received from the location sensor, so as to generaterespective mapped regions of the simulated surface, to delineate, basedon the simulated surface and the respective mapped regions, one or moreunmapped regions of the simulated surface, and to configure thesimulated surface of the body cavity to indicate the delineated unmappedregions.

There is further provided, in accordance with an embodiment of thepresent invention, a computer software product operated in conjunctionwith a probe that is configured for insertion into a body cavity of apatient and includes a location sensor for measuring a location of adistal end of the probe inside the body cavity, the product including anon-transitory computer-readable medium, in which program instructionsare stored, which instructions, when read by a computer, cause thecomputer to capture, from an imaging system, a three-dimensional (3D)image of a body cavity, to construct, using the captured 3D image, asimulated surface of the body cavity, to map, while, inserting the probeinto the body cavity, multiple positions within respective regions ofthe body cavity, in response to multiple location measurements receivedfrom the location sensor, so as to generate respective mapped regions ofthe simulated surface, to delineate, based on the simulated surface andthe respective mapped regions, one or more unmapped regions of thesimulated surface, and to configure the simulated surface of the bodycavity to indicate the delineated unmapped regions.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure is herein described, by way of example only, withreference to the accompanying drawings, wherein:

FIG. 1 is a schematic pictorial illustration of a catheter-tissuecontact visualization system for a force-sensing catheter, in accordancewith an embodiment of the present invention;

FIG. 2 is a flow diagram that schematically illustrates a method ofmapping a cardiac chamber, in accordance with an embodiment of thepresent invention;

FIG. 3 is a schematic detail view showing a distal tip of a catheter incontact with endocardial tissue of the cardiac chamber, in accordancewith an embodiment of the present invention; and

FIG. 4 is a schematic pictorial illustration of an image presented onthe catheter-tissue contact visualization system, in accordance with anembodiment of the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS Overview

Physiological or anatomical mapping procedures typically create a mapcomprising map points collected from an electroanatomical mappingsystem. Each map point comprises a respective coordinate within a bodycavity, and possibly a physiological property collected by a medicalprobe at the respective coordinate. While mapping a body cavity such asa chamber of a heart, the map may have resolutions that vary from regionto region. The variation can be based on the number of measurementscollected for a particular region used to generate the map.

Embodiments of the present invention provide methods and systems forvisualizing unmapped regions of the body cavity. In some embodiments,the unmapped regions may be determined by subtracting the mapped regionsfrom an image of the body cavity that has been pre-acquired using, forexample, magnetic resonance imaging or computer tomography. By conveyingvisual feedback delineating non-mapped regions of the body cavity,embodiments of the present invention can provide, to a medicalprofessional performing a medical procedure, a visual guide indicatingany unmapped regions of the body cavity that need to be mapped duringthe medical procedure.

System Description

FIG. 1 is a schematic, pictorial illustration of an intracardiac mappingsystem 20 that implements visualization of catheter-tissue contact, inaccordance with an embodiment of the present invention. System 20comprises a probe 22, such as an intracardiac catheter, and a controlconsole 24. In embodiments described hereinbelow, it is assumed thatprobe 22 is used for diagnostic or therapeutic treatment, such as formapping electrical potentials in a heart 26 of a patient 28.Alternatively, probe 22 may be used, mutatis mutandis, for othertherapeutic and/or diagnostic purposes in the heart or in other bodyorgans.

An operator 30 inserts probe 22 through the vascular system of patient28 so that a distal end 32 of probe 22 enters a chamber of heart 26.Console 24 typically uses magnetic position sensing to determineposition coordinates of distal end inside heart 26. To determine theposition coordinates, a driver circuit 34 in console 24 drives fieldgenerators 36 to generate magnetic fields within the body of patient 28.Typically, field generators 36 comprise coils, which are placed belowthe patient's torso at known positions external to patient 28. Thesecoils generate magnetic fields in a predefined working volume thatcontains heart 26. A magnetic field sensor (also referred to herein aslocation sensor 38) within distal end 32 of probe 22 generateselectrical signals in response to these magnetic fields. A signalprocessor 40 processes these signals in order to determine the positioncoordinates of distal end 32, typically including both location andorientation coordinates. The method of position sensing describedhereinabove is implemented in the above-mentioned CARTO™ system and isdescribed in detail in the patents and patent applications cited above.

Location sensor 38 transmits a signal to console 24 that is indicativeof the location coordinates of distal end 32. Location sensor 38 maycomprise one or more miniature coils, and typically comprises multiplecoils oriented along different axes. Alternatively, location sensor 38may comprise either another type of magnetic sensor, or positiontransducers of other types, such as impedance-based or ultrasoniclocation sensors. Although FIG. 1 shows a probe with a single locationsensor, embodiments of the present invention may utilize probes withmore than one location sensor.

In an alternative embodiment, the roles of location sensor 38 andmagnetic field generators 36 may be reversed. In other words, drivercircuit 34 may drive a magnetic field generator in distal end 32 togenerate one or more magnetic fields. The coils in generator 36 may beconfigured to sense the fields and generate signals indicative of theamplitudes of the components of these magnetic fields. Processor 40receives and processes these signals in order to determine the positioncoordinates of distal end 32 within heart 26.

Although in the present example system 20 measures the position ofdistal end 32 using magnetic-based sensors, other position trackingtechniques may be used (e.g., impedance-based sensors). Magneticposition tracking techniques are described, for example, in U.S. Pat.Nos. 5,391,199, 5,443,489, 6,788,967, 6,690,963, 5,558,091, 6,172,4996,177,792, whose disclosures are incorporated herein by reference.Impedance-based position tracking techniques are described, for example,in U.S. Pat. Nos. 5,983,126, 6,456,864 and 5,944,022, whose disclosuresare incorporated herein by reference.

In embodiments described herein, processor 40 is configured to collectimage data from a medical imaging system (not shown) such as a magneticresonance imaging (MRI) system, or a computed tomography (CT) system, ora probe mapping system such as the CARTO™ mapping system produced byBiosense Webster Inc., of Diamond Bar, Calif. As described hereinbelow,processor 40 uses the image data to construct a simulated surface of thecardiac chamber in question.

Processor 40 typically comprises a general-purpose computer, withsuitable front end and interface circuits for receiving signals fromprobe 22 and controlling the other components of console 24. Processor40 may be programmed in software to carry out the functions that aredescribed herein. The software may be downloaded to console 24 inelectronic form, over a network, for example, or it may be provided onnon-transitory tangible media, such as optical, magnetic or electronicmemory media. Alternatively, some or all of the functions of processor40 may be carried out by dedicated or programmable digital hardwarecomponents.

An input/output (I/O) interface 42 enables console 24 to interact withprobe 22. Based on the signals received from probe 22 (via interface 42and other components of system 20), processor 40 drives a display 44 topresent operator 30 with an image 46 showing the position of distal end32 in the patient's body, as well as status information and guidanceregarding the procedure that is in progress.

Probe 22 also comprises a force sensor 48 contained within distal end32. Force sensor 48 measures a force applied by a distal tip 50 of probe22 to the endocardial tissue of heart 26 by generating a signal to theconsole that is indicative of the force exerted by the distal tip on theendocardial tissue. In one embodiment, the force sensor may comprise amagnetic field transmitter and receiver connected by a spring in distalend 32, and may generate an indication of the force based on measuringthe deflection of the spring. Further details of this sort of probe andforce sensor are described in U.S. Patent Application Publications2009/0093806 and 2009/0138007, whose disclosures are incorporated hereinby reference. Alternatively, distal end 32 may comprise another type offorce sensor.

Additionally or alternatively, system 20 may comprise an automatedmechanism (not shown) for maneuvering and operating probe 22 within thebody of patient 28. Such mechanisms are typically capable of controllingboth the longitudinal motion (advance/retract) of probe 22 andtransverse motion (deflection/steering) of distal end 32 of the probe.In such embodiments, processor 40 generates a control input forcontrolling the motion of probe 22 based on the signals provided by themagnetic field sensor in the probe.

In order to map the cardiac chamber in question, operator 30 advancesprobe 22 so that distal tip 50 engages endocardial tissue at multiplelocations, and processor 40 “registers” the multiple locations on thesimulated surface produced from the image data. Thus, the systemcollects multiple map points, with each map point comprising acoordinate on the inner chamber surface. In embodiments of the presentinvention, processor 40 can use signals received from force sensor 48 todetect when distal tip 50 is in contact with the endocardial tissue.

In alternative embodiments, probe 22 may comprise an electrode 54coupled to the distal end and configured to function as animpedance-based position transducer. Additionally or alternatively,electrode 54 can be configured to measure a certain physiologicalproperty (e.g., the local surface electrical potential) at each of themultiple locations. In some embodiments, system 20 can correlate theposition measurements and the electrical potential measurements. Inother words, system 20 can collect multiple map points, with each mappoint comprising a coordinate on the inner chamber surface and arespective physiological property measurement at this coordinate.

During the diagnostic treatment, processor 40 presents image 46 of thesimulated surface, with the registered location measurements laidthereon (the fusion of the simulated surface and the locationmeasurements is referred to herein as a map), to operator 30 on display44, and stores data representing the image in a memory 52. Memory 52 maycomprise any suitable volatile and/or non-volatile memory, such asrandom access memory or a hard disk drive. After collecting the imagedata, processor 40 applies an algorithm (e.g., a fast mapping process)to construct image 46. In the present embodiment, image 46 comprises asimulated 3D surface (e.g., a polygon mesh) of a surface of the cardiacchamber, which processor 40 presents as image 46 on display 44. In someembodiments, operator 30 can manipulate image 46 using one or more inputdevices 54.

Although FIG. 1 shows a particular system configuration, other systemconfigurations can also be employed to implement embodiments of thepresent invention, and are thus considered to be within the spirit andscope of the present invention. For example, the methods describedhereinbelow may be applied using position transducers of types otherthan the magnetic field sensor described above, such as impedance-basedor ultrasonic location sensors. The term “position transducer” as usedherein refers to an element mounted on probe 22 which causes console 24to receive signals indicative of the coordinates of the distal end. Theposition transducer may thus comprise a receiver on the probe, whichgenerates a position signal to the control unit based on energy receivedby the transducer; or it may comprise a transmitter, emitting energythat is sensed by a receiver external to the probe. Furthermore, themethods described hereinbelow may similarly be applied in therapeuticand diagnostic applications using not only catheters, but also probes ofother types, both in the heart and in other body organs and regions.

Simulated Surface Visualization

FIG. 2 is a flow diagram that schematically illustrates a method ofmapping a chamber of heart 26, FIG. 3 is a schematic detail view showingdistal tip 50 in contact with endocardial tissue 80 of heart 26, andFIG. 4 is a schematic pictorial illustration of image 46 comprising asimulated surface 90, in accordance with an embodiment of the presentinvention in accordance with an embodiment of the present invention.While the example shown in FIGS. 2-4 describe mapping a chamber of heart26, embodiments of the present invention can be used to map any bodycavity within patient 28.

In a capture step 60, processor 40 captures (i.e., receives) a threedimensional (3D) image of a chamber of heart 26, and in a constructionstep 62, the processor uses the 3D image to construct simulated surface90 in memory 52. As described supra, processor 40 can collect the 3Dimage from a MRI or a CT system.

In an insertion step 64, operator 30 inserts probe 22 into a chamber ofheart 26 (also referred to herein as the cardiac chamber), and advancesthe probe so that distal tip 50 engages endocardial tissue 80 and exertsforce F on the endocardial tissue, as shown in FIG. 3. To verify contactbetween distal tip 50 and endocardial tissue, processor 40 receivesforce measurements from force sensor 48 that indicate force F. In anacquire step 66, while distal tip 50 presses against endocardial tissue80, processor 40 automatically acquires location measurements fromlocation sensor 38 indicating a current position of distal end 32.

In response to the location and the force measurements, processor 40, ina mapping step 68, maps the location measurement to a given region ofthe simulated surface. In operation, upon detecting distal tip 50engaging endocardial tissue 80 at multiple locations, processor 40 canmap each of the multiple locations to a corresponding region of thesimulated surface without any intervention from the operator.

In a delineation step 70, the processor delineates any unmapped regionsin the cardiac chamber. In addition to delineating one or more unmappedregions in the cardiac chamber, as processor 40 receives force andposition measurements from probe 22, the processor can delineaterespective mapped regions of the simulated surface.

In embodiments where processor 40 receives the location measurementsfrom magnetic field sensor 38, the processor can map the receivedmagnetic field measurements to corresponding locations on the simulatedsurface. In embodiments where processor 40 receives the locationmeasurements from electrode 54, the location measurements comprisingimpedances to a current transmitted through the electrode, the processorcan map the received impedance measurements to corresponding locationson the simulated surface. Additionally or alternatively, processor canuse first location measurements received from magnetic field sensor tocalibrate second location measurements received from electrode 54.

In some embodiments, processor 40 can delineate the unmapped region(s)by subtracting the respective mapped regions from the simulated surface.Additionally, processor 40 can delineate mapping resolutions fordifferent mapped regions of the simulated surface. In embodiments of thepresent invention a given mapping resolution for a given regioncomprises a number of positions mapped in the given region usingembodiments described hereinabove. In other words, if the cardiacchamber comprises first and second regions having similarly sizedsurface areas, and the first region has ten positions mapped and thesecond region has six positions mapped, then the mapping resolution ofthe first region is higher than the mapping resolution of the secondregion.

In a configuration step 72, processor 40 configures simulated surface 90to indicate the mapped and the unmapped regions of the cardiac chamber,and in a presentation step 74, the processor presents, on display 44,image 46 comprising the simulated surface. In the example shown in FIG.4, image 46 comprises both mapped regions 92 and unmapped regions 94. Inalternative embodiments, image 46 may comprise either mapped regions 92or unmapped regions 94 (i.e., one or the other).

To configure simulated surface 90, processor 40 can associate a firstvisual design with the unmapped regions, and overlay the first visualdesign on the unmapped regions of the simulated surface. Additionally,processor 40 can associate a second visual design with the mappedregions, and overlay the second visual design on the mapped regions ofthe simulated surface. In some embodiments, the visual design maycomprise a shading or an intensity. In alternative embodiments, thevisual design may comprise or visual patterns 98 and 100, as shown inFIG. 4.

Additionally, processor 40 can present a legend 96 that details visualpatterns 98 and 100 that the processor can use when presenting themapped and the unmapped regions. In the example shown in FIG. 4, legend96 comprises unmapped pattern and multiple mapped patterns 100, whereineach mapping resolution (or each range of mapping resolutions) has arespective mapped pattern 100. In other words, while presentingsimulated surface 90, processor 40 overlays unmapped pattern 98 on theunmapped regions and overlays the respective mapped pattern 100 for eachof the mapped regions, thereby conveying visual feedback to operator 30for the procedure that is in progress.

Finally, in a comparison step 76, if additional locations in the cardiacchamber need to be mapped, then operator 30 repositions catheter 22 andthe method continues with step 66. However, if no additional locationsare needed, then mapping the cardiac chamber is complete, and the methodends.

The corresponding structures, materials, acts, and equivalents of allmeans or steps plus function elements in the claims below are intendedto include any structure, material, or act for performing the functionin combination with other claimed elements as specifically claimed. Thedescription of the present disclosure has been presented for purposes ofillustration and description, but is not intended to be exhaustive orlimiting to the disclosure in the form disclosed. Many modifications andvariations will be apparent to those of ordinary skill in the artwithout departing from the scope and spirit of the disclosure. Theembodiment was chosen and described in order to best explain theprinciples of the disclosure and the practical application, and toenable others of ordinary skill in the art to understand the disclosurefor various embodiments with various modifications as are suited to theparticular use contemplated.

It will be appreciated that the embodiments described above are cited byway of example, and that the present invention is not limited to whathas been particularly shown and described hereinabove. Rather, the scopeof the present invention includes both combinations and subcombinationsof the various features described hereinabove, as well as variations andmodifications thereof which would occur to persons skilled in the artupon reading the foregoing description and which are not disclosed inthe prior art.

The invention claimed is:
 1. An apparatus comprising: a display; a probeconfigured for insertion into a body cavity of a patient and comprisinga location sensor for measuring a position of a distal end of the probeinside the body cavity; and a processor; wherein the apparatus isconfigured: to receive a three-dimensional image of at least part of abody cavity, the three-dimensional image comprising an image from one ofa magnetic resonance imaging system and a computed tomography system; toconstruct a simulated surface of at least part of said body cavity usingsaid three-dimensional image, and to show the simulated surface on thedisplay; after constructing said simulated surface, to receive signalsfrom the location sensor of the probe, the signals comprising a seriesof locations of the probe inside said body cavity; when the probe islocated inside said body cavity, to map at least a portion of the bodycavity corresponding to said simulated surface, the mapping processcomprising: (i) when a tip of the probe is positioned against a bodycavity tissue, determining that the tip is positioned against the bodycavity tissue; and then (ii) determining a position of the tip of theprobe against the body cavity tissue using the location sensor in theprobe; and then (iii) mapping said position of the tip of the probeagainst the body cavity tissue with respect to the simulated surface,and visually marking said position of the tip of the probe as a mappedregion of the simulated surface on the display by overlaying one of aplurality of different mapped visual designs on a corresponding area ofthe simulated surface, (iii) a. wherein mapped regions remain markedwith one of said plurality of mapped visual designs at least untilcompletion of the mapping process; (iii) b. wherein areas of thesimulated surface which remain unmapped are visually indicated asunmapped by overlaying a first visual design on corresponding areas ofthe simulated surface unless and until the unmapped areas are mapped;and (iii) c. wherein the apparatus is configured to perform said mappingand visual marking steps automatically in response to the probe tipbeing positioned against the body cavity tissue; and (iv) repeatingsteps (i)-(iii) a plurality of times when the tip of the probe islocated in a series of different positions in the body cavity with thetip of the probe positioned against body cavity tissue; the apparatusbeing further configured so that when the apparatus performs saidmapping process: at least some regions of the simulated surface whichhave been visually marked as being mapped on the display during saidmapping process are further modified during the course of the mappingprocess to visually indicate changing mapping resolution as additionaltip positions are mapped; mapping resolution corresponds to a quantityof different positions in a region of the simulated surface which havebeen mapped by the mapping process; and said plurality of mapped visualdesigns comprise a plurality of visually distinguishable mappingpatterns on the display, each corresponding to different respectivemapping resolutions.
 2. The apparatus according to claim 1, theapparatus being further configured to present a legend on the display,the legend comprising the first visual design and the plurality ofmapped visual designs, the plurality of mapped visual designs comprisinga range of mapping patterns corresponding to different mappingresolutions.
 3. The apparatus of claim 1, the apparatus being furtherconfigured to simultaneously show on the display: areas of the simulatedsurface having the first visual design, indicating unmapped areas; areasof the simulated surface having a mapped visual design (x) indicatingmapped areas; and areas of the simulated surface having a differentmapped visual design (y) indicating mapped areas which have a differentmapping resolution than said area having said mapped visual design (x).4. The apparatus of claim 3, the apparatus being further configured sothat when the mapping process is performed: when the tip of the probe islocated in a different second position in the body cavity where the tipis positioned against body cavity tissue, and wherein a correspondingportion of the simulated surface has previously been marked as mapped onthe display using a mapped visual design (x) indicating a first mappingresolution; then in said corresponding portion of the simulated surface,the mapped visual design (x) indicating the first mapping resolution isreplaced with the different mapped visual design (y), the differentmapped visual design (y) indicating a different and higher mappingresolution than mapped visual design (x).
 5. The apparatus of claim 1:wherein the probe is an intracardiac catheter adapted for use inside aheart.
 6. The apparatus of claim 1: wherein the probe comprises amagnetic field sensor at the tip thereof.
 7. The apparatus of claim 1:wherein the apparatus comprises a table, and a plurality of fieldgenerators positioned under the table.
 8. The apparatus of claim 1:wherein the catheter comprises a force sensor; and wherein the apparatusis configured to determine that the tip of the catheter is positionedagainst the body cavity tissue in response to a force measurement fromthe force sensor during the mapping process.
 9. The apparatus of claim1, the apparatus being further configured to simultaneously show aplurality of different mapped visual designs on the display, and whereinsaid plurality of mapped visual designs differ from each other as to atleast one of a shading, an intensity, and a pattern.
 10. The apparatusof claim 1: wherein the location sensor of the probe comprises anelectrode, the electrode being configured to measure impedances to acurrent transmitted through the electrode.
 11. The apparatus of claim 1,wherein the processor is functionally linked to one of a magneticresonance imaging system, and a computed tomography system, and isconfigured to receive three-dimensional image data therefrom.
 12. Theapparatus of claim 1: further comprising a non-transitory computerreadable medium holding computer software instructions; wherein saidcomputer software instructions, when executed by the processor, causethe apparatus to perform steps of said mapping process.
 13. Theapparatus of claim 1: wherein the location sensor of the probe comprisesat least one of: a plurality of coils oriented along different axes, animpedance-based location sensor, and an ultrasonic location sensor. 14.The apparatus of claim 1: wherein the probe further comprises anelectrode configured to measure a physiological property, and whereinthe apparatus is adapted to save a plurality of physiological propertymeasurements in correlation with a plurality of corresponding probelocation coordinates on the body cavity.
 15. A computer softwareproduct, operated in conjunction with an imaging arrangement comprisinga computer processor, a display, and a probe, the probe being configuredfor insertion into a body cavity of a patient and comprising a locationsensor for measuring a location of a distal end of the probe inside thebody cavity, the software product comprising a non-transitorycomputer-readable medium, in which program instructions are stored,which program instructions, when read by a computer processor, cause theimaging arrangement to: retrieve a three-dimensional image of at leastpart of a body cavity; construct a simulated surface of at least part ofsaid body cavity using said three-dimensional image, and show thesimulated surface on the display; after constructing said simulatedsurface, with the probe inside a body cavity, to map at least a portionof the body cavity corresponding to said simulated surface by a mappingprocess, the mapping process comprising: (i) with a tip of the probe ispositioned against a body cavity tissue, determining that the tip ispositioned against the body cavity tissue; (ii) determining a positionof the tip of the probe against the body cavity tissue using thelocation sensor in the probe; (iii) mapping said position of the tip ofthe probe while it is against the body cavity tissue with respect to thesimulated surface, and visually marking said position of the tip of theprobe as a mapped region of the simulated surface on the display byoverlaying one of a plurality of different mapped visual designs on acorresponding area of the simulated surface, (iii) a. wherein mappedregions remain marked with one of said plurality of mapped visualdesigns at least until completion of the mapping process; (iii) b.wherein areas of the simulated surface which remain unmapped arevisually indicated as unmapped by overlaying a first visual design oncorresponding areas of the simulated surface unless and until theunmapped areas are mapped; and (iii) c. wherein the apparatus isconfigured to perform said mapping and visual marking stepsautomatically in response to the probe tip being positioned against thebody cavity tissue; and (iv) repeating steps (i)-(iii) a plurality oftimes when the tip of the probe is located in a series of differentpositions in the body cavity with the tip of the probe positionedagainst body cavity tissue; wherein when the mapping process isperformed by the imaging arrangement according to said programinstructions: at least some regions of the simulated surface which havebeen visually marked as being mapped on the display during said mappingprocess are further modified during the course of the mapping process tovisually indicate changing mapping resolution as additional tippositions are mapped; mapping resolution corresponds to a quantity ofdifferent positions in a region of the simulated surface which have beenmapped by the mapping process; and said plurality of mapped visualdesigns comprise a plurality of visually distinguishable mappingpatterns on the display, each corresponding to different respectivemapping resolutions.
 16. The computer software product of claim 15,wherein when the mapping process is performed by the imaging arrangementaccording to said program instructions, the imaging arrangementsimultaneously shows on the display: areas of the simulated surfacehaving the first visual design, indicating unmapped areas; areas of thesimulated surface having a mapped visual design (x) indicating mappedareas; and areas of the simulated surface having a different mappedvisual design (y) indicating mapped areas which have a different mappingresolution than said area having said mapped visual design (x).
 17. Thecomputer software product of claim 15, wherein when the mapping processis performed by the imaging arrangement according to said programinstructions: when the tip of the probe is located in a different secondposition in the body cavity where the tip is positioned against bodycavity tissue, and wherein a corresponding portion of the simulatedsurface has previously been marked as mapped on the display using amapped visual design (x) indicating a first mapping resolution; then insaid corresponding portion of the simulated surface, the mapped visualdesign (x) indicating the first mapping resolution is replaced with thedifferent mapped visual design (y), the different mapped visual design(y) indicating a different and higher mapping resolution than mappedvisual design (x).
 18. The computer software product of claim 15:wherein the software product is configured for use with a catheter whichcomprises a force sensor; and wherein when the mapping process isperformed by the imaging arrangement according to said programinstructions, the imaging arrangement determines that the tip of thecatheter is positioned against the body cavity tissue in response toreceiving a force measurement from the force sensor during the mappingprocess.
 19. A method, comprising: capturing a three-dimensional imageof at least part of a body cavity; constructing a simulated surface ofat least part of said body cavity using said three-dimensional image,and showing the simulated surface on a display; inserting a probe havinga location sensor into said body cavity; with the probe inserted insidesaid body cavity, mapping at least a portion of said body cavitycorresponding to said simulated surface, the mapping process comprising:(i) moving a tip of the probe to a position in the body cavity where thetip is positioned against a body cavity tissue, and determining that thetip is positioned against the body cavity tissue; (ii) determining aposition of the tip of the probe while it is against the body cavitytissue using the location sensor in the probe; (iii) mapping saidposition of the tip of the probe against the body cavity tissue withrespect to the simulated surface, and visually marking said position ofthe tip of the probe as a mapped region of the simulated surface on thedisplay by overlaying one of a plurality of different mapped visualdesigns on a corresponding area of the simulated surface, (iii) a.wherein mapped regions remain marked with one of said plurality ofmapped visual designs at least until completion of the mapping process;(iii) b. wherein areas of the simulated surface which remain unmappedare visually indicated as unmapped by overlaying a first visual designon corresponding areas of the simulated surface unless and until theunmapped areas are mapped; and (iii) c. wherein said mapping and visualmarking takes place automatically in response to the probe tip beingpositioned against the body cavity tissue; (iv) moving the tip of theprobe to a different position in the body cavity where the tip ispositioned against body cavity tissue; and (v) repeating steps (i)-(iv)a plurality of times; further: wherein at least some regions of thesimulated surface which have been visually marked as being mapped on thedisplay during said mapping process are further modified during thecourse of the mapping process to visually indicate changing mappingresolution as additional tip positions are mapped; wherein mappingresolution corresponds to a number of different positions in a region ofthe simulated surface which have been mapped by the mapping process; andwherein said plurality of mapped visual designs comprise a plurality ofvisually distinguishable mapping patterns each corresponding todifferent respective mapping resolutions.
 20. The method of claim 19,the method comprising simultaneously showing on the display: (a) areasof the simulated surface having the first visual design, indicatingunmapped areas; (b) areas of the simulated surface having a mappedvisual design (x) indicating mapped areas; and (c) areas of thesimulated surface having a different mapped visual design (y) indicatingmapped areas which have a different mapping resolution than said areahaving said mapped visual design (x); the method further comprisingmoving the tip of the probe to a second position in the body cavitywhere the tip is positioned against body cavity tissue, and thendetermining that the tip is positioned against the body cavity tissue ina region of the body cavity which has previously been mapped, wherein acorresponding portion of the simulated surface has previously beenmarked as mapped on the display using a mapped visual design (x)indicating a first mapping resolution; and then in an area of thesimulated surface corresponding to said second position in the bodycavity, replacing the mapped visual design (x) indicating the firstmapping resolution with the different mapped visual design (y), thedifferent mapped visual design (y) indicating a different and highermapping resolution.